1.2 Observational Studies vs. Designed Experiments
Term
Definition
Example(s)
Observational
Study
Experimental
Study
Explanatory
Variable
Response
Variable
Confounding
Variable
Lurking
Variable
1
Cross-sectional
Study
Case-controlled
Study
Cohort
Study
2

1.1 Introduction to the Practice of Statistics
Term
Statistics
Descriptive
Statistics
Inferential
Statistics
Population
Sample
Individual
Variable
Definition
Example(s)
Parameter
Statistic
Qualitative
Variable
Quantitative
Variable
Discrete
Variable
Conti

4.1 Scatter Diagrams & Correlations
Association: there is a relationship between two variables
Positive Association: as one variable increases, the other variable increases
Negative Association: as one variable increases, the other variable decreases
Line

3.3 Measures of Central Tendency & Dispersion from Grouped Data
Class Midpoint: average the lower class limit and the upper class limit
Population Mean ( ) and Sample Mean ( x ): xi is the class midpoint, f is the
frequency, and n is the number of classes

2.1 Organizing Qualitative Data
Frequency Distribution: gives the number of items in each category
Relative Frequency Distribution: gives the proportion of each category relative to
the total number of items
Bar Graph: a horizontal or vertical representat

3.2 Measures of Dispersion
Range: the difference between the largest and the smallest data value
Population Standard Deviation ( ): the square root of the sum of squared
deviations about the population mean divided by the number of observations
=
( x i )

3.4 Measures of Position & Outliers
z-score: represents the distance that a data value is from the mean in terms of
the number of standard deviations
Population z-score: z =
x
Sample z-score: z =
x x
s
If x > x , the z-score is positive.
If x = x , the z-

3.5 The Five-Number Summary & Boxplots
Five-Number Summary: min, Q1, Q2, Q3, max
Distribution Shape
Symmetric
Skewed right (positive)
Skewed left (negative)
Table 1
Comparing Distributions
1. Which sex has the higher median?
2. Which sex has the greater s

3.1 Measures of Central Tendency
Population Mean (): computed by adding all of the values of the variable in the
population and dividing by the number of observations (quantitative data only &
best to use if the frequency distribution is roughly symmetric

4.2 Least-Squares Regression
Least-Squares Regression Line: a line of best fit that always travels through the
point ( x , y ). The LSR line minimizes the sum of the squared residuals and is
often labeled ^y , y hat. Each point on the LSR line represents